GTM: Standalone versus LTM/GTM Combo?

As I've hit a brick wall with stability on a GTM design I was working on, I thought I'd reach out to the community for some advice on where to go from here. I know the GTM fairly well as a standalone appliance, but I was curious if there are any users utilizing GTM/LTM on the same appliance, and the pros/cons of such an implementation.